METTL14 knockdown alleviates inflammation in oral lichen planus by driving macrophage M2 polarization through...

Background Oral lichen planus (OLP) is a prevalent chronic disease affecting the oral mucosa, and its pathogenesis remains not fully understood. This study aims to examine the regulatory mechanism of METTL14/FDX1 in the development of OLP. Methods Macrophage polarization and METTL14/FDX1 expression were analyzed in mucosal tissues from OLP patients and controls via immunofluorescence, RT-qPCR, and ELISA. In vitro, THP-1-derived macrophages were transfected with METTL14 or FDX1 targeting/overexpression vectors to assess their roles in polarization (flow cytometry) and cytokine secretion (ELISA). The METTL14-FDX1 interaction and m6A modification were confirmed by RIP and MeRIP-PCR. Functional outcomes were evaluated in a macrophage-keratinocyte co-culture system (flow cytometry) and in an imiquimod-induced OLP mouse model treated with sh-METTL14. Results The abnormal accumulation of M1 macrophage was identified in mucosa of OLP patients. Upregulation of m6A-related key enzyme METTL14 was identified in macrophages of OLP patients, which was associated with inflammation of OLP. Mechanically, METTL14 knockdown reduced mRNA stability of FDX1 through m6A modification, thereby limiting the transcriptional expression of FDX1 in macrophage. Functionally, METTL14 overexpression promoted macrophage M1 polarization through upregulating FDX1. Additionally, macrophages with METTL14 knockdown inhibited keratinocytes apoptosis by polarizing to M2. In vivo, METTL14 knockdown alleviated inflammation in OLP mouse model by driving macrophage M2 polarization. METTL14, via upregulating FDX1, also promoted the production of T-helper cell-associated inflammatory cytokines (IFN-γ, IL-17) integral to OLP pathology. Conclusion METTL14 knockdown alleviates inflammation in OLP by driving macrophage M2 polarization through mediating FDX1 m6A modification.